Dust suppression of potash salts



United States Patent Olhce 3,393,973 Patented July 23, 1968 3,393,973 DUST SUPPRESSION F POTASH SALTS Adrian L. Almy, Carlsbad, N. Mex., assignor to International Minerals & Chemical Corporation, a corporation of New York No Drawing. Filed Dec. 15, 1965, Ser. No. 514,112

. 13 Claims. (Cl. 23-89) This invention relates to a method for the control of dusting of potash products. More particularly the invention relates to the treatment of hot, finely divided, inorganic potash salts to substantially reduce or prevent dusting. L i v The problem of controlling dust created by the handling of finely divided potash materials has been anniversal problem. When loading or unloading such materials in large quantities, the dust thus created causespoor working conditions,rloss of a large portion of'the prod-. uct and possible contamination of surrounding areas. For example, when loading a freightcar with finely divided potash material, it is frequently necessary for theoperator of theloading apparatus to wear a dust mask for protection. Sometimes the dust becomes so dense during loading and'unloading'operations, it is necessary to temporarily cease operation until the dust has settled. This results not-only ina loss of time but also an increase in operating costs.'

The problem of controlling the dusting of potash material is complicatedby the light color of the material and by the necessity of future processing of the material. It will be apparent that'means to prevent dusting of potash material desirably will not substantially adversely affect the color of the material and will not change the characteristics of the material to substantially affect subsequent processing.

In accordance withthe prior art, it has been possible to alleviate dusting by treating potash salts at substantially ambient temperatures with selected petroleum fractions. Thus, in accordance with U.S. Patent 3,063,800, finely divided potash salts are contacted with a relatively small amount of a viscous mineral oil which conforms to specifications set forth in the patent. The potash material treated in accordance with the aforesaid patent, when subjected to normal handling incident to loading and unloading operations, exhibits excellent freedom from dusting. Further, the color integrity of the material is maintained.

It has been found, however, that the technique of the aforesaid patent is applicable only in connection with potash salts at ambient temperatures, or at relatively low elevated temperatures. In the manufacture of potash salts such as langbeinite (2MgSO -K SO potassium sulfate and potassium chloride, a wet material is produced in the form of a flotation concentrate, filter cake, or the like, which product is dried (as in a conventional rotary drier) before being loaded or transported to product storage. The potash salt emerges from the driers at temperatures generally in the range from 300 to 350 F. It has been found that prior art dust control compositions such as those disclosed in the aforementioned U.S. Patent 3,063,800, are entirely unsatisfactory for use on a hot product.

It is an object of this invention to provide a method 7 for controlling the dusting of finely-divided potash salts.

It is another object of this invention to provide a method for the treatment of potash salts at elevated temperatures, whereby dusting of the salt is prevented.

Yet another object of this invention is to provide a substantially dust-free potash product.

Still another object of this invention is to provide a more effective technique for handling finely-divided potash salts.

Briefly, the method of the instant invention comprises controlling the dusting of finely-divided, inorganic, potash salts which comprises treating the potash salt at an elevated temperature in the range of 250 to 400 F. with a tall oil fraction in the amount of about 1 to 8 pounds per ton of said potash salt to substantially coat said potash salts with said tall oil fraction.

The potash salts susceptible to treatment in accordance with the instant invention are langbeinite, leonite, potassium chloride, potassium sulfate and similar simple or complex inorganic salts of potassium ordinarily employed as fertilizer ingredients which commonly create severe dusting problems. The process is carried out by applying to hot potash salts at an elevated temperature in a range of 250-400 F., about 1 to about 8 pounds per ton of potash salts, and more preferably about 3 to 5 pounds per ton of said potash salts, of a tall oil fraction. Commercial tall oil is an oily resinous mixture of rosin acids, fatty acids, sterols of high molecular weight, and unsaponifiables. The nature and proportions of the constituent varies widely and is not well known. Tall oil is ordinarily distilled to produce a variety of tall oil fractions. It has been found that such tall oil fractions are useful in carrying out the process of this invention. Exemplary of the tall oil fractions which have been found suitable for carrying out the process of the instant invention are tall oil pitch, tall oil heads, and distilled tall oil. The use of tall oil pitch is especially preferred because it provides a highly satisfactory process and product, and because it is relatively inexpensive.

Treatment of the hot potash salt may be accomplished in any manner which will provide a substantially even distribution of the tall oil fraction throughout the potash material. The treatment will advantageously be applied to the potash immediately after the hot, dry potash salts emerge from the drying operation. This permits increased convenience and flexibility in the handling of the potash salts prior to loading or storage, and prevents dusting problems which would otherwise occur in handling the potash salt. After the drying operation, and while the potash salt is still hot, commercial spray apparatus is advantageously employed to apply the tall oil fraction. A thin layer of potash salt on a moving belt can be sprayed with a tall oil fraction to achieve the object of this inven tion. It will be apparent that other means can also be employed to coat the potash salt and provide the coated product of this invention.

In one desirable method of application langbeinite, at the discharge from the drier operation and at a temperature of about 300 F., is treated with tall oil pitch as hereinbefore described, by discharging the potash salts from the drier on to a moving belt and spraying the potash with tall oil pitch as it moves along the belt. The potash is then discharged into a conventional loading hopper. Optionally, the treated langbeinite is passed through a screw conveyor where an additional mixing is provided and a more homogeneous coating is obtained. A preferred TALL OIL PITCH Characteristic Preferred Typical Range Specification Color (Gardner, 1933) 10% in benzene 15-18 17 Acid Value 55-70 60 Saponilication Value 110-140 130 Composition:

Moisture, percent 0. 1

Ash, perccnt 0.

Rosin Acids, percent. 20-33 26 Unsaponiiiables, percent 27-3ti 32 Fatty Acids, percent. 30-45 37 Softening Point, C 35 Specific Gravity, 25/25 C- 1. 010 Weight Per Gallon 25 0., lbs 8. 41 Viscosity, SFS, 210 F 104 Flash Point, Open Cup, F 495 Fire Point, Open Cup, F 545 EXAMPLE As an example of the method and product of the instant invention langbeinite recovered as a flotation concentrate is dried in a conventional rotary drier under conditions to provide a substantially moisture-free product, at a temperature of about 300 F. The langbeinite is discharged from the drier onto a moving belt, sprayed with tall oil pitch having a typical specification substantially as shown in the above table, in the amount of 4 pounds per ton of langbeinite. The treated salt is discharged from the belt conveyor to a screw conveyor, and then transported onto a loading hopper. The salt, upon cooling, is found to be substantially dust-free and non-caking. The individual particles of langbeinite are found to be coated with an extremely thin film of tall oil pitch. It is observed that the very fine particles have been bonded to the larger particles by the tall oil pitch.

It has been found that tall oil pitch is effective for dusting suppression when applied to other potash salts as described in the foregoing example. Such other salts include potassium sulfate and potassium chloride. It has further been found that satisfactory results are not obtainable when the potash salts are at an elevated temperature in excess of 400 F. The preferred temperature of operation is in the range of from 300-850 F.

It has further been found that many other treating materials such as petroleum fractions, polyether alcohols, gas oil, alkyl phenyl polyethylene glycol, fractionator bottoms, and hydraulic oils are unsatisfactory when substituted for the tall oil fraction. With such materials either satisfactory dust suppression is not achieved, or excess fuming and/or fire hazard occurs in the treatment step. Inexplicable, all of these materials have been found reasonably effective in treating potash salts for dust suppression at ambient temperatures, but they fail in treatment at elevated temperatures in excess of about 250 F.

While the invention has been described with reference to preferred embodiments and has been illustrated by specific examples,.it will be. understood that within the scope of the appended claims, the invention can be practiced other than as specifically described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of controlling dusting of finely-divided, inorganic potash salts which comprises treating said potash salt at a temperature in the range of about 250 F. to about 400 F. with about 1 to about 8 pounds of a tall oil fraction of the group consisting of tall oil pitch, tall oil heads, distilled tall oil and mixtures thereof, per ton of said potash salt to substantially coat said hot potash salt with said tall oil fraction.

2. The method in accordance with claim 1 in which the temperature of said potash salt is in the range of about 300 F. to about 350 F.

3. The method in accordance with claim 1 in which said tall oil fraction is applied in the amount of about 3 to 5 pounds per ton of said potash salt.

4. The method in accordance with claim 3 in which said tall oil fraction comprises tall oil pitch.

5. The method in accordance with claim 4 in which said potash salt is potassium sulfate. I

6. The method in accordance with claim 4 in which said potash salt is potassium chloride.

7. The method in accordance with claim 4 in which said potash salt is langbeinite.

8. A non-dusting potash salt consisting essentially of finely divided inorganic potash salt coated with about 1 to about 8 pounds per ton of said salt of a tall oil fraction of the group consisting of tall oil pitch, tall oil heads, distilled tall oil, and mixtures thereof.

9. A product in accordance with claim 8 in which said tall oil fraction is present in the amount of about 3 to 5 pounds per ton of said potash salt.

10. A product in accordance with claim 8 in which said tall oil fraction is tall oil pitch.

11. A product in accordance with claim 10 in which said potash salt is potassium sulfate.

12. A product in accordance with claim 10 in which said potash salt is potassium chloride.

13. A product in accordance with claim 10 in which said potash salt is langbeinite.

References Cited UNITED STATES PATENTS 2,234,484 3/1941 Weinig 23-89 2,734,002 2/1956 Schoeld et a1 23-89 XR 3,063,800 11/1962 Dancy 23-89 OSCAR R. VERTIZ, Primary Examiner. E. STERN, Assistant Examiner. 

